#!/bin/perl5

use strict;
use warnings;
use HTML::TokeParser;

my $str = q|<img src=\"test.jpg\"> highlight the word <img src=\"word.jpg\">|;

my $tp = HTML::TokeParser->new(\$str)
  or die "Couldn't parse $str: $!";

$tp->unbroken_text(1);
  
my ($html, $start);

while (my $tag = $tp->get_token) {
	
  if ($tag->[0] eq 'T'){
    my $t = $tag->[1];
    $t =~ s|word|<b>WORD</b>|g;
    $html .= $t;
  }
  else{
    $html .= $tag->[4] if $tag->[0] eq 'S';
    $html .= $tag->[1] if $tag->[0] eq 'C';
    $html .= $tag->[2] if $tag->[0] eq 'E';
  }

}

print "$html\n";

__DATA__
---------- Capture Output ----------
> "C:\Perl\bin\perl.exe" parse_str.pl

<img src=\"test.jpg\"> highlight the <b>WORD</b> <img src=\"word.jpg\">

> Terminated with exit code 0.